The present invention is directed to a cup-like dust guard cap for covering the opening for drilling tools in the tool holder in a hand-held drill. The guard includes a casing secured on the tool holder and a cover member with a through-opening for the tool. The cover member includes a seal for the tool as it extends through the guard into the tool holder.
Dust guard caps of the type described above protect the tool holders in hand-held drills and such tool holders are relatively sensitive to dirt such as from drillings and drill dust generated in the drilling operation.
Despite the use of resilient or elastic materials, such as rubber or the like, the known dust guard caps have had the disadvantage of sharply limited radial expandability at the through-opening. As a result, one dust guard cap is suitable only for a small range of tool diameters. Accordingly, for smaller diameter tools there is the problem of unsatisfactory sealing, while with larger diameter tools considerable friction is developed. Moreover, excessive stretching of the dust guard occurs for large diameter tools and results in damage.
Accordingly, dust guard caps with a through-opening in the cover part are known and the rim of the opening is provided with radially arranged slots. These slots improve the expandability of the through-opening so that a greater range of tool diameters can be accommodated. The disadvantage of this type of dust guard cap is insufficient sealing for the range of tool diameters used, because drill dust and drillings enter the tool holder through the slots.